An integral sub-assembly of most rotary driven tools, such as surgical drills, are their chuck assemblies. The chuck assembly is the part of the tool that holds a cutting accessory. For example, the cutting accessories used with surgical drills are drill bits, burs and wires. A typical chuck assembly includes a housing which contains a drive spindle. A set of jaws, also located in the housing, are mounted to the drive spindle. A linkage assembly opens and closes the jaws so that they can be used to grasp the accessory the tool is employed to drive. Once the accessory is mounted to the chuck assembly, the rotational power developed by a shaft of the motor internal to the tool is transferred through the drive spindle to the accessory. Providing rotary driven tools with chucks makes it possible to use these tools with many different types of cutting accessories.
In recent years, it has become popular to provide rotary driven tools with keyless chuck assemblies. A keyless chuck assembly is designed so that, when the chuck housing is held stable and its drive spindle is rotated, the jaws move together or move apart. Keyless chuck assemblies replace older, keyed chucks that require a key to lock and unlock the chuck jaws. One particular application in which keyless chuck assemblies are particularly popular is their use with powered surgical drills. An advantage of providing a surgical tool with keyless chuck is that it eliminates the need to bring a key into the surgical suite. Still another advantage of providing a keyless chuck is that this type of chuck is typically easier and quicker to lock and unlock than the keyed chucks that preceded it.
While keyless chucks have proven useful in surgical suites and in other environments where powered tools are used, there are some limitations associated with many currently available chucks. For example, in order to lock or unlock a chuck when it is attached to a tool, it is necessary to simultaneously hold the chuck housing stable while actuating the tool in order to cause the rotation of the drive spindle. When the chuck jaws fully close, lock tight against the complementary cutting accessory, the motive force generated by the tool is abruptly transferred to the chuck housing. Since the individual is still holding the housing, this individual is subjected to a physical jolt. Sometimes this jolt can be so great that it causes the gloves of the person holding the tool to tear. Once this tearing occurs, the individual must leave the surgical field.
Recently, at least in the surgical environment, it has become desirable to provide chuck assemblies to which a cutting accessory has already been preloaded. These chuck assemblies are provided with spindles that are readily couplable into the drills with which they are used. Once the assembly is separated from the drill, a technician rotates the spindle while holding the chuck housing stable in order to cause the desired locking/unlocking movement of the chuck jaws. One benefit of a removable chuck is that the technician changing cutting accessories is not subjected to the shock associated with the power locking/unlocking of the chuck. Another advantage of this arrangement is that chucks can be preloaded with cutting accessories to allow the surgeon rapidly switch the cutting accessory that is being used to perform a surgical procedure.
However, there is some difficulty associated with manual locking/unlocking currently available chucks. This difficulty is due to the fact that the drive spindle of a chuck is a relatively small and thin component, less than 0.4 inches (1.0 cm) wide and less than 2 inches (5.0 cm) long. Consequently, it is not easy for an individual to get a good grip on this component in order to turn it or hold it static in order to accomplish the desired locking of the associated jaws. This, in turn, has made it difficult for surgical personnel to provide surgeons with chuck assemblies with cutting accessories that have already been locked in place for use.